pub fn odd_fibnacci_sum(threshold: u32) -> u32 {
    let mut res = 0u32;
    let (mut x, mut y) = (0u32, 1u32);
    while y < threshold {
        let z = x + y;
        if y % 2 == 1 {
            res += y;
        }
        x = y;
        y = z;
    }
    res
}
